There are two kinds of frame structures in the Long Term Evolution (LTE) system. The frame structure type 1 is suitable for the Frequency Division Duplex (FDD) of the full duplex and the half duplex. As shown in FIG. 1, the length of each radio frame is 10 ms, made up of 20 slots, and each slot is 0.5 ms, which is numbered from 0 to 19. A subframe is made up of two continuous slots; for example, the subframe i is made up of two continuous slots 2i and 2i+1. No matter it is the half duplex FDD or the full duplex FDD, the uplink and the downlink are transmitted at different frequencies; while for the half duplex FDD, the UE cannot send and receive data at the same time; while there is no such restriction for the full duplex FDD, that is, there can be 10 downlink and 10 uplink subframes in every 10 ms interval. The frame structure Type 2 is suitable for the Time Division Duplex (TDD). As shown in FIG. 2, the length of a radio frame is 10 ms, made up of two half-frame with the length of 5 ms. One half-frame is made up of 5 subframes of which the length is 1 ms. The supported uplink and downlink configuration is shown in Table 1; “D” in the table shows that the subframe is a downlink subframe, “U” shows that the subframe is an uplink subframe, and “S” shows that the subframe is a special subframe. The special subframe is made up of a downlink pilot time slot (DwPTS), a guard period (GP) and an uplink pilot time slot (UpPTS), and the total length is 1 ms. Each subframe i is made up of two slots 2i and 2i+1 of which the lengths are 0.5 ms (15360*Ts).
The frame structure Type 2 supports two kinds of downlink-uplink switching cycles, 5 ms and 10 ms. In the uplink-downlink switching cycle of 5 ms, both of two half-frames have the special subframes. In the uplink-downlink switching cycle of 10 ms, only the first half-frame has the special subframe. The subframes 0, 5 and DwPTS are always reserved for the downlink transmission. The UpPTS and the next subframe which is adjacent to the special subframe are always reserved for the uplink transmission. Therefore, for the uplink-downlink switching cycle of 5 ms, the UpPTS, the subframe 2 and the subframe 7 are reserved for the uplink transmission; and for the uplink-downlink switching cycle of 10 ms, the UpPTS and the subframe 2 are reserved for the uplink transmission.
TABLE 1uplink and downlink configurationUplinkswitchingandcycledownlinkfromconfig-downlinkSubframe numberurationto uplink012345678905 msDSUUUDSUUU15 msDSUUDDSUUD25 msDSUDDDSUDD310 ms DSUUUDDDDD410 ms DSUUDDDDDD510 ms DSUDDDDDDD65 msDSUUUDSUUD
The LTE defines the following three kinds of downlink physical control channels: Physical Control Format Indicator Channel (PCFICH); Physical Hybrid Automatic Retransmission Request Indicator Channel (PHICH); Physical Downlink Control Channel (PDCCH).
Wherein, the information borne by the PCFICH is used to indicate the number of the Orthogonal Frequency Division Multiplexing (OFDM) symbol of the PDCCH transmitted in a subframe, and it is sent in the first OFDM symbol of the subframe, and the frequency location where it is located is determined by the system downlink bandwidth and the cell identity (ID). The PHICH is used to bear the acknowledgement/negative acknowledgement feedback information of the uplink transmission data. The number of the PHICH and the time and frequency location is determined by the system message and the cell ID in the Physical Broadcast Channel (PBCH) of the downlink carrier where the PHICH is located. The PDCCH is used to bear the Downlink Control Information (DCI), including: scheduling information of the Physical Uplink Shared Channel (PUSCH), scheduling information of the Physical Downlink Shared Channel (PDSCH), and the uplink power control information.
Since the LTE-Advanced network needs to be able to access the LTE users, its operation frequency band needs to cover the current LTE frequency band; there is no assignable spectral bandwidth of continuous 100 MHz in that frequency band, so one technology that the LTE-Advanced needs to solve is to aggregate several continuous component carriers (CC, frequency spectrum) distributed in different frequency bands together by adopting the Carrier Aggregation (CA) technology, to form the 100 MHz bandwidth which can be used by the LTE-Advanced. One component carrier can be regarded as a Cell too. In a plurality of component carriers aggregated by the terminal, the high layer will configure one pair of uplink/downlink component carrier therein as the primary uplink/downlink component carrier (PCell or PCC). Other component carriers are called the secondary component carriers (SCell or SCC). The LTE R10 standard defines that the physical uplink control channel can only be sent in the primary uplink component carrier.